Armature-winding



2 Sheets-Sheet 1.

(No Model.)

D. P. THOMSON. ARMATURE WINDING.

No. 533,930. Patented Feb. 12, 1895.

wrrgcsscs UNITED STATES PATENT OFFICE.

DAVID P. THOMSON, OF SOHENEOTAD Y, NEIV YORK, ASSIGNOR TO THE GENERALELECTRIC COMPANY, OF BOSTON, MASSACHUSETTS.

ARMAT-URE-WINDING.

SPECIFICATION forming part of Letters .Patent No. 533,930, datedFebruary 12, 1895. Application filed August 4:, 1'8 94. Serial No.519A96. (No model.)

To all whom it may concern:

Be it known that I, DAVID P. THOMSON, a

, citizen of the-United States, residing at Schenfor dynamo-electricmachines, and more specifically to the connections between the coils andthe segments of the commutator in direct current machinery; and has forits object to provide a method of and means for cross-com necting thewindings, as it is commonly called, so as to reduce the potential andreduce the number of volts per bar in the commutator.

In cases Where the maximum number of commutator bars permissible by thewinding have been tapped 0E, and the number is yet not enough to reducethe volts per bar to a working value, it is usual to interpolatebarsbetween those connected to the winding and to divide the lead fromeach coil so that it will deliver to two bars at corresponding points onthe commutator, thus dividing the potential of adjacent bars to one halfand giving double the number of com mutator segments.

In the construction of certain types of dynamo-electric armatures, it isfound imperative to limit the number of volts per bar delivered to thecommutator so as to avoid sparking at the brushes. This effectuallyremoves the trouble experienced from sparking due to too high voltageper bar. In doing this it introduces a new difiiculty in that, ascommonly connected, the leads to the commutator bars from the coils areof diiterent lengths, and thus, as the resistance and selfinduction ofthe two paths are different, the electro-motive force delivered to eachof two different bars in a pair is also different. In armaturesdeveloping large currents, the difficulty presented by these differencesof lead may become avery serious one, and it is this particulardifficulty which my invention aims to overcome. To accomplish thispurpose I make the leads to the two segments of equal or approximatelyequal length; and this I accomplish by taking the lead from the coil orbar of. the armature first to a point equidistant from the two segmentsof the commu tator to which it is to be connected, and at this pointbranching the lead and carrying one-half of it to each segment, thusaffording a perfect remedy for the particular difficulty pointed outabove.

The accompanying drawings show illustrations of my invention, Figures 1and 2 being end views of armatures and commutators, as herein described,Fig. 1 showing my invention applied to an eight-pole machine and Fig. 2as applied to one of six poles. Fig. 3 is a view of the particularconnector which I have devised to carry out the purpose of my invention,and Fig. 4 is a modification thereof.

Referring to Fig. 1, A is the armature. B is the commutator. O, O, 0 Oare the commutator brushes. D, D, &c.,are the poles of the machinewhich, as already pointed out, is an eight-pole machine of common type.The field-magnet windings are not shown, but may be of any desired type.E, F, G, H, I, K, L show respectively groups of armature bars each ofwhich may be taken as a type of a coil of any kind desired by theengineer, my improved connection being applicable either to coilwindings or bars. M, N, O, P are the junction or branching points of theleads, as already herein pointed out. The individual armature bars arelettered with the small letters corresponding to the large letterdesignating the group, as e, 6', 6 (be. I have not illustrated thenegative brushes upon the commutator because the nuinberof linesrequired for their connections would confuse the drawing unnecessarily.The dotted lines in the drawings show the connections upon the back orpulley end of the armature. It will be sufficient in illustrating myinvention to point out the connections for two sets of armature bars,for which purpose I have selected those lettered e andf respectively.The branching pointfor the connections of these bars is at M. The arrowsshow the direction of the current. \Vith the individual connections areshown lines of difierent character, as will be readily understood fromthe drawings, the heavy lines showing the connections to the coils whichare being commutated. Starting from the barf, the current passes to thej unction point m, and thence by the heavy lines to the sections 5, 5,upon the commutator, part of the path to the junction point on being incommon and the paths from thejunction point on to the commutator beingof equal or approximately equal length. Similarly, starting from the barf" the junction point m is reached by a common lead and thence bydivided leads to the commutator bars 3, 3. It will be unnecessary totrace the connections further, as they are all made in the same way.

Referring to Fig. 2, I illustrate the same system of connections asapplied to a six-pole machine, and its application will be apparent fromthe description of Fig.1 without further explanation.

In Fig. 3, Q represents the connection from the armature bars to thecommon junction point (as at M), and Q, represents a similar connectorto the two commutator bars with which the coils are to be joined.

Fig. 4 shows a modification of the connection which I have devised,being substantially similar except that the connections to thecommutator segments are of different lengths, but of the sameresistance, which I accomplish by making the shorter arm Of of theconnection of a higher resistance metal than the arm Q. Thismodification however is not preferred, inasmuch as the inductance of theparts Q and Q would be different and would give rise in some degree tothe objections already pointed out, although they would be materiallylessened by this construction.

The arrangement of leads which I have described has what I denominate acushioning effect, inasmuch as the resistance of the leads is very muchhigher than that of the coils which they connect to the commutatorsegments, and this tends to the equal distribution of current and addsto the efficiency of the windin In series windings the difficulty ofdistribution of current among a number of different commutator segmentsconnected to the same armature coil has been a great objection to themethod of interpolating segments as a means of reducing the potentialper bar; and so far as I have been aware, in the endeavor to keep theresistance of the armature at a minimum, the leads have also been madeof low resistance and generally of unequal length, giving rise to thetroubles which I have heretofore pointed out, which are particularlygreat in case the load is thrown suddenly off the machine, the sparkingwhich follows in such cases often resulting in serious damage to thecommutator. The method which I have devised, therefore, of making theseleads of a higher resistance than the armature coils, and also of makingthem of substantially equal resistance and inductance, has to a greatextent obviated these objections to a series wound armature generat inglarge currents; and it is this method of distributing the currentbetween the armature bars which I have devised and which I seek toprotect especially.

What I claim as new, and desire to secure by Letters Patent of theUnited States, is-

1. The method of distributing current between a number of segmentsconnected to a common coil in a series armature winding, which consistsin making the leads from the coil to such segments of a higherresistance than the coil, and of substantially equal resistance.

2. The method of distributing current between a number of commutatorsegments connected to a common coil in a series armature winding, whichconsists in making the leads from such segments to the coil of higherresistance than the coil and of substantially equal resistance andinductance.

3. In a dynamo-electric machine, cross-connections for thecommutator-segments,such cross-connections consisting of a lead from thearmature coil to a point equidistant from the commutator segments to beconnected thereto, and additional leads from such points to thecommutator segments, substantially as set out herein.

4. In combination, in a dynamo-electric machine, armature coils andcommutator segments, the segments cross-connected to the coils by leadsof equal lengths, as herein set out.

5. In combination, in a dynamo-electric machine, armature coils, acommutator having a plurality of segments for each armature coil, andleads of equal lengths from the commutator-segments to the coil,substantially as described.

6. In a series wound dynamo-electric machine, armature coils, acommutator having a plurality of segments for each armature coil, a leadfrom each armature coil to a point equidistant from the segments towhich it is to be connected, and leads from such point to the severalcommutator-segments, thus forming from each armature coil to itsappropriate commutator-segments leads of substantially equal resistanceand self-induction, as herein set out.

In witness whereof I have hereunto set my hand this 18th day of July,189i.

.DAVID P. THOMSON.

'Witnesses:

B. B. HULL, A. F. DIACDONALD.

